Cats are generally territorial and very sensitive animals, often feeling insecure. They also retain a natural instinct for survival in the wild. If something suddenly appears behind a cat without its knowledge, it will naturally be startled and fly away. If you observe the animated GIFs circulating online of cats being frightened by cucumbers or bananas, you'll notice a common thread.
The problem is that cat owners sometimes sneak cucumbers out to scare their cats when they're not looking, cucumbers that weren't originally in the cat's sight. If you try a different approach, like slowly appearing in front of your cat and then offering a cucumber, you'll find that the cat doesn't care at all and isn't startled. Actually, this isn't just a cat's experience; humans also have this sense of danger. If you turn around and see someone suddenly appear behind you, you'll be startled too.
